1. Field of the Invention
This invention relates to metal oxide solid acids useful as catalysts for the polymerization of a feed stream containing at least one of pure monomer, C5 monomers, and C9 monomers to produce a hydrocarbon resin, to processes of preparing hydrocarbon resins using solid acid catalysts, and to hydrocarbon resins produced by such processes.
2. Discussion of Background
Hydrocarbon resins are low molecular weight, thermoplastic materials prepared via thermal or catalytic polymerization. The resins may be derived from several different sources of monomers. The monomer sources include cracked petroleum distillate from oil refining, turpentine fractions (e.g., terpenes from natural product distillation), paper mill by-product streams, coal tar, and a variety of pure olefinic monomers.
The resulting hydrocarbon resins can range from viscous liquids to hard, brittle solids with colors ranging from water white to pale yellow, amber, or dark brown depending on the monomers used and the specific reaction conditions. Typically, pure monomer resins tend to be water white, C9 monomer resins tend to be brown, and C5 monomer resins tend to be yellow.
Hydrocarbon resins are used extensively as modifiers in adhesives, rubber, hot-melt coatings, printing inks, paint, flooring, and other applications. The resins are usually used to modify other materials.
Pure monomer hydrocarbon resins can be prepared by cationic polymerization of styrene-based monomers such as styrene, alpha-methyl styrene, vinyl toluene, and other alkyl substituted styrenes using Friedel-Crafts polymerization catalysts such as Lewis acids (e.g., boron trifluoride (BF.sub.3), complexes of boron trifluoride, aluminum trichloride (AlCl.sub.3), alkyl aluminum chlorides).
Similarly, aliphatic C5 hydrocarbon resins can be prepared by cationic polymerization of a cracked petroleum feed containing C5 and C6 paraffins, olefins, and diolefins also referred to as "C5 monomers". These monomer streams are comprised of cationically polymerizable monomers such as 1,3-pentadiene which is the primary reactive component along with cyclopentene, pentene, 2-methyl-2-butene, 2-methyl-2-pentene, cyclopentadiene, and dicyclopentadiene. The polymerizations are catalyzed using Friedel-Crafts polymerization catalysts such as Lewis acids (e.g., boron trifluoride (BF.sub.3), complexes of boron trifluoride, aluminum trichloride (AlCl.sub.3), or alkyl aluminum chlorides). In addition to the reactive components, nonpolymerizable components in the feed include saturated hydrocarbons which can be codistilled with the unsaturated components such as pentane, cyclopentane, or 2-methylpentane. This monomer feed can be copolymerized with C4 or C5 olefins or dimers as chain transfer agents.
Also, aromatic C9 hydrocarbon resins can be prepared by cationic polymerization of aromatic C8, C9, and/or C1 unsaturated monomers derived from petroleum distillates resulting from naphtha cracking and are referred to as "C9 monomers". These monomer streams are comprised of cationically polymerizable monomers such as styrene, alpha-methyl styrene, beta-methyl styrene, vinyl toluene, indene, dicyclopentadiene, divinylbenzene, and other alkyl substituted derivatives of these components. The polymerizations are catalyzed using Friedel-Crafts polymerization catalysts such as Lewis acids (e.g., boron trifluoride (BF.sub.3), complexes of boron trifluoride, aluminum trichloride (AlCl.sub.3), alkyl aluminum chlorides). In addition to the reactive components, nonpolymerizable components include aromatic hydrocarbons such as xylene, ethyl benzene, cumene, ethyl toluene, indane, methylindane, naphthalene and other similar species. These nonpolymerizable components of the feed stream can be incorporated into the resins via alkylation reactions.
Although Lewis acids are effective catalysts for the cationic polymerization reactions to produce hydrocarbon resins, they have several disadvantages. Conventional Lewis acids are single use catalysts which require processing steps to quench the reactions and neutralize the acids.
Further, conventional Lewis acids also require removal of catalyst salt residues from the resulting resin products. Once the salt residues generated from the catalyst neutralization are removed, the disposal of these residues presents an additional cost. Therefore, it is of particular interest to reduce the amount of catalyst residues, particularly halogen-containing species generated in these reactions.
Another problem involved in using conventional Lewis acid catalysts, such as AICI.sub.3 and BF.sub.3, is that they are hazardous materials. These conventional Lewis acid catalysts generate highly corrosive acid gases on exposure to moisture, (e.g., HF, HCl).
In addition to the traditional Lewis acids, work has been done with certain solid acid catalysts. BITTLES et al., "Clay-Catalyzed Reactions of Olefins. I. Polymerization of Styrene", Journal of Polymer Science: Part A, Vol. 2, pp. 1221-31 (1964) and BITTLES et al., "Clay-Catalyzed Reactions of Olefins. II. Catalyst Acidity and Measurement", Journal of Polymer Science: Part A, Vol. 2, pp. 1847-62 (1964), the disclosures of which are herein expressly incorporated by reference in their entirety, together disclose polymerization of styrene with acid clay catalysts to obtain polymers having molecular weights between 440 and 2000 as determined by freezing point depression of benzene solutions. These documents disclose that the catalyst was prepared for polymerization by heating under vacuum, and that if the catalyst adsorbed moisture, the activity of the catalyst could be restored by reheating under vacuum.
SALT, "The Use of Activated Clays as Catalysts in Polymerisation Processes, with Particular Reference to Polymers of Alpha Methyl Styrene", Clay Minerals Bulletin, Vol. 2, pp. 55-58 (1948), the disclosure of which is herein incorporated by reference in its entirety, discloses polymerization of styrene and/or alpha-methyl styrene by using a clay catalyst to obtain polymers that range from dimers to molecular weights of about 3000.
U.S. Pat. No. 5,561,095 to CHEN et al., the disclosure of which is herein incorporated by reference in its entirety, discloses a supported Lewis acid catalyst for polymerization of olefins, including C3-C23 alpha-olefins, to obtain polymers having number average molecular weights (Mn) ranging from about 300 to 300,000. Exemplary Lewis acid supports include silica, silica-alumina, zeolites, and clays. Example 1 of CHEN et al. discloses that a Lewis acid supported on silica is heated under vacuum.
U.S. Pat. No. 3,799,913 to WHEELER et al., the disclosure of which is herein incorporated by reference in its entirety, discloses Friedel-Crafts catalysts for polymerization of polymerizable constituents, including alpha-methyl styrene, indene, vinyl toluene and styrene, to obtain polymers having a number average molecular weight (Mn) ranging from about 350 to 1200. Zinc chloride is disclosed as one of the Friedel-Crafts catalysts.
U.S. Pat. No. 3,652,707 to SAINES, the disclosure of which is herein incorporated by reference in its entirety, discloses Friedel-Crafts metal halide catalysts for polymerization of olefin hydrocarbons, including pentene, styrene and methylstyrene, to obtain polymers having a molecular weight of from about 700 to about 2500. Zinc chloride is disclosed as one of the Friedel-Crafts metal halide catalysts.
PENG et al., "Electrophilic Polymerization of 1,3-Pentadiene Initiated by Aluminum Triflate", Eur. Polym. J, Vol. 30, No. 1, pp. 69-77 (1994), the disclosure of which is herein incorporated by reference in its entirety, discloses aluminum triflate for polymerization of piperylene to obtain polymers having varying number average molecular weights.
European Patent Application 0 352 856 A1, the disclosure of which is herein incorporated by reference in its entirety, discloses use of aluminum triflate, cerium triflate, e.g., for oligomerization of C3 to C6 olefins to obtain oligomers having 6 to 24 carbon atoms.
GANDINI et al., "The Heterogeneous Cationic Polymerization of Aromatic Monomers by Aluminum Triflate", Polymer Preprints, American Chemical Society, pp. 359-360 (1996), the disclosure of which is herein incorporated by reference in its entirety, discloses use of aluminum triflate for polymerization of C9 related monomers to obtain a polymer having a number average molecular weight (Mn) around 3000. This document also discloses that aluminum triflate could be useful for the direct "resinification"of mixtures of aromatic monomers and solvents arising from specific petroleum cuts.
Other documents, the disclosures of which are herein incorporated by reference in their entireties, which generally disclose the use of solid acid catalysts to polymerize monomers for the preparation of resins include U.S. Pat. No. 4,068,062 to LEPERT, U.S. Pat. No. 4,130,701 to LEPERT, U.S. Pat. No. 4,245,075 to LEPERT, and U.S. Pat. No. 4,824,921 to LUVINH.